title: Localization of Prp8, Brr2, Snu114 and U4/U6 proteins in the yeast tri-snRNP by electron microscopy.
abstract: The U4/U6-U5 tri-small nuclear ribonucleoprotein (snRNP) is a major, evolutionarily highly conserved spliceosome subunit. Unwinding of its U4/U6 snRNA duplex is a central event of spliceosome activation that requires several components of the U5 portion of the tri-snRNP, including the RNA helicase Brr2, Prp8 and the GTPase Snu114. Here we report the EM projection structure of the Saccharomyces cerevisiae tri-snRNP. It shows a modular organization comprising three extruding domains that contact one another in its central portion. We have visualized genetically tagged tri-snRNP proteins by EM and show here that U4/U6 snRNP forms a domain termed the arm. Conversely, a separate head domain adjacent to the arm harbors Brr2, whereas Prp8 and the GTPase Snu114 are located centrally. The head and arm adopt variable relative positions. This molecular organization and dynamics suggest possible scenarios for structural events during catalytic activation.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.
authors.forename: Irina
authors.initials: I
authors.lastname: Häcker
authors.forename: Bjoern
authors.initials: B
authors.lastname: Sander
authors.forename: Monika M
authors.initials: MM
authors.lastname: Golas
authors.forename: Elmar
authors.initials: E
authors.lastname: Wolf
authors.forename: Elif
authors.initials: E
authors.lastname: Karagöz
authors.forename: Berthold
authors.initials: B
authors.lastname: Kastner
authors.forename: Holger
authors.initials: H
authors.lastname: Stark
authors.forename: Patrizia
authors.initials: P
authors.lastname: Fabrizio
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lührmann
mesh_terms: D004789:Enzyme Activation; D046911:Macromolecular Substances / Q000737:chemistry; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D017381:Spliceosomes / Q000235:genetics / Q000378:metabolism
chemical_list: D046911:Macromolecular Substances; C491451:PRP31 protein, S cerevisiae; C065573:PRP6 protein, S cerevisiae; C077018:PRP8 protein, S cerevisiae; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017415:Ribonucleoprotein, U5 Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C472240:SNU114 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C104158:BRR2 protein, S cerevisiae; D020365:RNA Helicases